multi-threaded nfsd, RPC SVCXPRT re-usage

During a discussion un the am-utils list, it emerged that the RPC library
apparantly doesn't allow one SVCXPRT to service two request in parallel
(e.g. accept a second before the first has been replied to) because the
structure contains (private) fields specific to a request.
How does the (threaded) NetBSD in-kernel NFS server deal with that?